Repair work conducted on high voltage electrical cables is typically conducted while current flows through the cables. Consequently, it is imperative that workers in contact with cables and crews on the ground remain at all times electrically isolated. In order to transfer objects from a crew on the ground to a worker in the air, non-conductive ropes are employed to ensure that the aerial worker is not electrically grounded and the ground crew is not in electrical contact with the cable. When ropes made of a resistive material such as hemp or nylon are in clean and new condition, they remain largely non-conductive. However, as such ropes become soiled, they can become dangerously conductive. Accordingly, it is necessary to periodically test the dielectric integrity of ropes in use by workers, to ensure that they remain safely non-conductive.
It will be understood that the term "rope" as used herein refers as well to straps, cords, and the like. It will be further understood that although reference is generally made herein to testers adapted to measure conductivity, with slight adaptations they may be used to measure resistivity.
Dielectric rope testers typically make electrical contact with a rope under test at two points a fixed distance apart, and measure the conductivity of the rope between the points. Such devices must grasp the rope tightly enough to make electrical contact at the two points. However, they should also permit the entire length of the rope, or a reasonable portion thereof, to be passed relatively quickly and easily through the device. Previous such devices have lacked a means to make secure electrical contact with a rope being passed through the device. Typically, such devices are provided with a pair of contacts, with the rope being simply placed on the contacts. The user has to ensure that the rope is making electrical contact with both contacts, and this can be a time-consuming operation when a long rope is being tested. As well, the user cannot be certain that the rope has in fact been properly tested, since there is no way of ensuring that the contacts have in fact contacted the rope.
In order to achieve reasonable ease of use and certainty of testing with a testing device, the device should be capable of easily and securely engaging and disengaging a rope under test. As well, it should be possible to pull the rope through the device continuously, with the conductivity of the segment of rope under test being measured on a continuous basis between the contacts.
Accordingly, it is an object of the present invention to provide a rope testing device that accurately measures the conductivity of a rope between two spaced-apart probes, wherein the probes are capable of easy and secure engagement to the rope, while permitting the rope to be pulled through the device continuously.